perf/x86: Implement cycles:p for SNB/IVB

Now that there's finally a chip with working PEBS (IvyBridge), we can
enable the hardware and implement cycles:p for SNB/IVB.

Cc: Stephane Eranian <eranian@google.com>
Requested-and-tested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1338884803.28282.153.camel@twins
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 43 insertions, 8 deletions

diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index 83794d8e6af0..7241e2fc3c17 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -365,6 +365,7 @@ struct x86_pmu {
         int             pebs_record_size;
         void            (*drain_pebs)(struct pt_regs *regs);
         struct event_constraint *pebs_constraints;
+        void            (*pebs_aliases)(struct perf_event *event);
 
         /*
          * Intel LBR
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 965baa2fa790..2312c1ff1b19 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1336,15 +1336,9 @@ static void intel_put_event_constraints(struct cpu_hw_events *cpuc,
         intel_put_shared_regs_event_constraints(cpuc, event);
 }
 
-static int intel_pmu_hw_config(struct perf_event *event)
+static void intel_pebs_aliases_core2(struct perf_event *event)
 {
-        int ret = x86_pmu_hw_config(event);
-
-        if (ret)
-                return ret;
-
-        if (event->attr.precise_ip &&
-            (event->hw.config & X86_RAW_EVENT_MASK) == 0x003c) {
+        if ((event->hw.config & X86_RAW_EVENT_MASK) == 0x003c) {
                 /*
                  * Use an alternative encoding for CPU_CLK_UNHALTED.THREAD_P
                  * (0x003c) so that we can use it with PEBS.
@@ -1365,10 +1359,48 @@ static int intel_pmu_hw_config(struct perf_event *event)
                  */
                 u64 alt_config = X86_CONFIG(.event=0xc0, .inv=1, .cmask=16);
 
+                alt_config |= (event->hw.config & ~X86_RAW_EVENT_MASK);
+                event->hw.config = alt_config;
+        }
+}
+
+static void intel_pebs_aliases_snb(struct perf_event *event)
+{
+        if ((event->hw.config & X86_RAW_EVENT_MASK) == 0x003c) {
+                /*
+                 * Use an alternative encoding for CPU_CLK_UNHALTED.THREAD_P
+                 * (0x003c) so that we can use it with PEBS.
+                 *
+                 * The regular CPU_CLK_UNHALTED.THREAD_P event (0x003c) isn't
+                 * PEBS capable. However we can use UOPS_RETIRED.ALL
+                 * (0x01c2), which is a PEBS capable event, to get the same
+                 * count.
+                 *
+                 * UOPS_RETIRED.ALL counts the number of cycles that retires
+                 * CNTMASK micro-ops. By setting CNTMASK to a value (16)
+                 * larger than the maximum number of micro-ops that can be
+                 * retired per cycle (4) and then inverting the condition, we
+                 * count all cycles that retire 16 or less micro-ops, which
+                 * is every cycle.
+                 *
+                 * Thereby we gain a PEBS capable cycle counter.
+                 */
+                u64 alt_config = X86_CONFIG(.event=0xc2, .umask=0x01, .inv=1, .cmask=16);
 
                 alt_config |= (event->hw.config & ~X86_RAW_EVENT_MASK);
                 event->hw.config = alt_config;
         }
+}
+
+static int intel_pmu_hw_config(struct perf_event *event)
+{
+        int ret = x86_pmu_hw_config(event);
+
+        if (ret)
+                return ret;
+
+        if (event->attr.precise_ip && x86_pmu.pebs_aliases)
+                x86_pmu.pebs_aliases(event);
 
         if (intel_pmu_needs_lbr_smpl(event)) {
                 ret = intel_pmu_setup_lbr_filter(event);
@@ -1643,6 +1675,7 @@ static __initconst const struct x86_pmu intel_pmu = {
         .max_period             = (1ULL << 31) - 1,
         .get_event_constraints  = intel_get_event_constraints,
         .put_event_constraints  = intel_put_event_constraints,
+        .pebs_aliases           = intel_pebs_aliases_core2,
 
         .format_attrs           = intel_arch3_formats_attr,
 
@@ -1885,6 +1918,7 @@ __init int intel_pmu_init(void)
 
                 x86_pmu.event_constraints = intel_snb_event_constraints;
                 x86_pmu.pebs_constraints = intel_snb_pebs_event_constraints;
+                x86_pmu.pebs_aliases = intel_pebs_aliases_snb;
                 x86_pmu.extra_regs = intel_snb_extra_regs;
                 /* all extra regs are per-cpu when HT is on */
                 x86_pmu.er_flags |= ERF_HAS_RSP_1;